Which subject did Margaret Thatcher study at Somerville College? Did she ever find work related to her degree?

Chemistry.

Margaret Thatcher (née Roberts; 1925-2013) was the first female Prime Minister (PM) of the United Kingdom, serving in that role from 1979 to 1990. She was the longest-serving British PM of the 20th century.

At Somerville College, Oxford (1943-47), Thatcher studied chemistry, specialising in X-ray crystallography where she was supervised by Dorothy Hodgkin (Nobel Prize winner.) Thatcher then worked for a time as a research chemist, before moving into law and then politics.

https://en.wikipedia.org/wiki/Margaret_Thatcher